The BD7Fx05EFJ-C (BD7F105EFJ-C, BD7F205EFJ-C) isolated flyback DC-DC converter was created by ROHM and is optimized for gate driver power supply in xEV applications, such as electric compressors and PTC heaters. The application size and effort for noise design countermeasures are decreased in its new product by using a circuit layout that gives steady switching frequency characteristics without the requirement for a photocoupler. The BD7Fx05EFJ-C eliminates the need for photocouplers, transformer auxiliary windings, and other auxiliary components typically required to monitor secondary-side voltage and current thanks to its superior analog design technology. In addition, by reducing the number of components, it has enabled increased miniaturization in addition to eliminating concerns with photocouplers, such as high power consumption, varying detection accuracy owing to temperature, and degradation over time. In comparison to conventional isolated flyback power supply circuits, it is therefore feasible to reduce by 10 the number of components—including the photocoupler—used for current sensing (corresponding to a board area of 30%).
Along with fixing the switching ON time, the device also offers an adaptive ON-time control feature that ensures a constant frequency of about 350 kHz independent of output power. As its new converters do not lie inside this band, noise countermeasures may be much reduced. To comply with the CISPR25 automobile EMC standard, considerable noise design in the frequency range from 150kHz to 300kHz is required. This reduces the amount of noise design efforts, together with a spread spectrum function that minimizes radiated noise. This innovative DC-DC converter IC is perfect for gate driver power supplies, such as industrial power supplies, PLCs, and inverters, as well as automobile electric compressors, PTC heaters, and inverters, which need to be safely isolated from the battery.
